1. Field of the Invention
The present invention relates to a detection apparatus applicable to a medical imaging apparatus, a non-destructive testing apparatus, an analysis apparatus using radiation, or the like, and also relates to a radiation detection apparatus and a radiation detection system.
2. Description of the Related Art
In recent years, great advances have been made in technology to produce a liquid crystal display panel using thin film transistors (TFTs), which has allowed it to achieve a large-sized display panel or a large-sized display screen. This technology is also applicable to production of a large-sized area sensor (detection apparatus) having a conversion element such as a photoelectric conversion element realized using semiconductor and a switch element such as a TFT. Such an area sensor may be combined with a fluorescent member to perform a wavelength conversion, i.e., to convert a radiation such as a X-ray into visible light or the like to be used as a radiation detection apparatus such as an X-ray detection apparatus. In general, the pixel structure used in the radiation detection apparatus can be classified into two types, i.e., a single-plane type in which a conversion element and a switch element are disposed in the same plane, and a stacked type in which a conversion element is disposed above (stacked onto) a switch element. In the production of the single-plane type pixels, the conversion element and the switch element can both be produced using the same semiconductor production process. This allows simplification of the production process. In the case of the stacked-type detection apparatus, the provision of the conversion element above the switch element makes it possible to increase the size of the conversion element in each pixel compared with the single-plane type. Therefore, the stacked-type detection apparatus is capable of providing a larger signal, a higher signal-to-noise ratio, and a higher sensitivity than can be provided by the single-plane type detection apparatus. In radiation detection apparatuses, in particular in medical X-ray detection apparatuses, there is a need for a reduction in the amount of radiation a patient is exposed to. To meet this requirement, it is important to achieve a sensor having high sensitivity and high signal-to-noise (S/N) ratio. Next, an explanation is given below as to noise. Noise is generated by many sources. Devices/elements that can be noise sources include conversion elements, switch elements, signal lines, integrating amplifiers, and peripheral circuits. Hereinafter, noise generated by a signal line will be referred to as signal line noise. When a signal line has parasitic capacitance C, the signal line noise is given by a following equation.Signal line noise=√kTC 
Hereinafter, noise generated by an integrating amplifier will be referred to as amplifier noise. In a case where an integrating amplifier with feedback capacitance Cf is used as a charge reading amplifier, the amplifier noise is given by the following equation.Amplifier noise=C/Cf×noise at amplifier input
Therefore, a reduction in parasitic capacitance C of the signal line is an effective approach to reduce noise of the detection apparatus. That is, to achieve high sensitivity, it is effective to reduce noise by reducing the parasitic capacitance of the signal line.
In the detection apparatus, there is also a need for an increase in driving speed. When a driving line via which a driving pulse is supplied to control turning-on/off of a switch element has capacitance Cg and resistance Rg, the time constant τ of this driving line is given by the following equation.τ=Cg×Rg 
Thus, if the capacitance and/or the resistance of the driving line increases, the time constant τ of the driving line increases. This can cause a driving pulse transmitted via the driving line to become dull or distorted. Therefore, if the turn-on period of the switch element is reduced, the dullness can make it difficult for the switch element to be in an on-state for a designed necessary period. That is, the dullness makes it difficult to reduce the turn-on period, which makes it difficult to increase the driving speed.
Japanese Patent Laid-Open No. 2002-76360 discloses a technique to realize a single-plane type radiation detection apparatus with signal/driving lines (hereinafter, referred to simply as lines) having reduced resistance. U.S. Patent Application No. 2009/0004768 proposes a technique to reduce resistance of an interconnection line in a stacked type radiation detection apparatus.
In detection apparatuses, there is a need for a reduction in pixel pitch, an increase in the number of pixels, an increase in sensitivity, and an increase in driving speed. In particular, medical X-ray detection apparatuses includes a wide variety of types such as an X-ray mammography apparatus, an X-ray transmission detecting apparatus capable of taking a moving image, etc., and a further reduction in pixel pitch and a further increase in the number of pixels are more seriously needed in these various types of medical X-ray apparatuses than in general X-ray detection apparatuses.
In such detection apparatuses, with reducing pixel pitch and increasing number of pixels, the number of interconnection lines and the number of intersects between signal lines and driving lines increase. As a result, capacitance associated with signal lines and driving lines increases. In particular, in a stacked-type detection apparatus such as that disclosed in U.S. Patent Application No. 2009/0004768, an increase also occurs in the number of intersects between signal lines and conversion elements, which causes a further increase in capacitance associated with signal lines. As a result, noise caused by the capacitance associated with the signal lines increases, which results in a reduction in sensitivity. Thus there is a need for a technique to reduce the noise by reducing the capacitance associated with the signal lines. It is also necessary to reduce the time constant associated with driving lines. Furthermore, in the stacked-type detection apparatus, it is necessary to take into account influences of intersects between driving lines and conversion elements as well as influences if intersects between signal lines and driving lines. In sum, in detection apparatuses, in particular in radiation detection apparatuses where the stacked-type pixel structure is employed, it is necessary to increase sensitivity and increase driving speed.